1. Field of the Invention
The invention is drawn to a method for decolorizing and/or deodorizing zein from corn products.
2. Description of the Prior Art
Zein is a protein by-product of corn processing which has many industrial uses and which can be incorporated into numerous commercial products, including paints and inks, coatings for food products, tableted medicaments, paper and paper products, microencapsulating agents, adhesives in laminated wood products, and bases for chewing gums. Zein exhibits adhesive properties and is soluble in aqueous alcohols and alkaline solutions, and may be used in the preparation of films and fibers. Films may be readily formed by spraying, dipping or otherwise coating the outer surface of objects with a solution of zein and drying. Such films have excellent resistance to water, acids, and heat, and also possesses electric insulation properties.
A variety of processes have been described for recovering and purifying zein from corn products, including extraction with aqueous alcohols, hydrocarbons or other organic solvents. However, the zein extracted by these processes, when dried, is characterized by an inherent yellow color and odor. These characteristics have deterred its use in some applications, particularly those in the food and medical industries. The yellow color of corn and zein has been attributed to the carotenoids β-carotene, zeaxanthin, and lutein (Quackenbush et al., 1961, J. Agric. Food Chem. 9:132-135; Blessin, 1962, Cereal Chem. 39:326-242; and Kurilich and Juvick, 1999, J. Agric. Food Chem. 47:1948-1955)
A number of authors have described processes for removing the impurities responsible for yellow coloration of zein (Mason and Palmer, 1934, J. Biol. Chem. 107:131-132; Swallen, 1938, U.S. Pat. No. 2,120,946; Pearce, 1941, U.S. Pat. No. 2,229,870; and Starling et al., 1951, GB patent specification no. 651,396). Of these, Starling et al. described decolorizing zein by contact of a zein solution with adsorbents selected from various activated carbons, activated alumina, Fuller's Earth, kieselguhr, bentonite, diatomaceous silica, and precipitated chalk, followed by treatment with a bleaching agent. More recently, Takahashi et al. (U.S. Pat. No. 5,367,055) described a process for removing color from zein by extraction with acetone, while McInnis et al. (U.S. Pat. No. 6,610,831) described a process for removing color from zein by extraction of flaked corn with ethanol followed by contact with an activated carbon adsorbent. None of these processes have addressed the removal of odor from zein products.
Therefore, despite these advances, the need remains for devising an improved process for recovering decolorized and deodorized zein product, that includes not only a zein product which is decolorized and deodorized while in solid phase, but which is also colorless in solution.